Making Manufacturing Sustainable For Chips

There is widespread agreement that fabs and manufacturers in general should operate in a sustainable way, but what exactly does that mean? And what concrete steps can fabs take toward that goal?

Once we get past the simplistic “more sustainable is better,” things tend to get pretty fuzzy. Consider the definition of sustainability itself. Corporate responsibility reports and similar documents often talk about “development that balances people, profit, and the planet.”

Like many broad statements, this one can be stretched to fit almost any practice that enhances the future health of the corporation. One corporate responsibility report that I reviewed devoted several pages to the company’s efforts to hedge against interest rate risk. Which is certainly good business practice, but doesn’t have much to do with a fab’s environmental impact. Another company detailed its commitment to fair hiring and safe working conditions, in both its own facilities and those operated by suppliers. Again, fair labor practices are a good thing, but aren’t necessarily relevant to energy consumption or greenhouse gas emissions.

An approach more in keeping with the idea of sustainability as related to environmental issues is lifecycle analysis. Consider all of the inputs to the fab and all of the outputs, and distribute them over the useful lives of the ultimate products. The fewer resources are consumed over the total product life, the more environmentally sustainable the product is.

This approach does have the virtue of being understandable by non-experts. It emphasizes the costs of rapid obsolescence and the benefits of product and material reuse. However, actually conducting the analysis and extracting the contributions of individual entities can be extremely difficult.

For example, a virgin silicon wafer is one of the most highly refined artifacts ever created by humans. Converting quartz sand to electronics-grade silicon consumes tremendous amounts of energy and involves highly toxic intermediate compounds. But how much of this expenditure is attributable to the semiconductor industry, given the parallel markets for solar-grade and metallurgical silicon? If a commodity memory chip and a high-end microprocessor both start with the same raw materials, can one be said to be “more sustainable” than the other?

At the other end of the supply chain, the amount of precious or toxic metal contained in a single smartphone or tablet is minute, and therefore extremely difficult to recover from a scrapped device. Multiplied by an entire industry that ships billions of devices, though, and the numbers add up. The EPA estimates that recycling 1 million cell phones can yield 24 kg of gold, 250 kg of silver, 9 kg of palladium, and more than 9,000 kg of copper. Worldwide, electronics waste accounts for more than 5% of municipal solid waste. What responsibility do semiconductor manufacturers have for the ultimate disposal of their products?

Making these questions even more complicated, remember that the industry supply chain is global. Silicon wafer manufacturing, fabrication of integrated circuits, assembly of electronic devices, and the ultimate consumer might be in four different countries, each with different regulations. The company whose name is on the device’s case may do very little actual manufacturing and may be located in a fifth country. This last company will often bear the brunt of consumer and investor displeasure if a supplier engages in questionable practices, while the supplier itself may face few consequences from its own investors or regulators.

Individual countries can regulate the parts of the supply chain within their borders, but doing so may simply shift the environmental burden (and jobs) to countries with less stringent regulatory regimes. Those countries are often poor, raising concerns that rich countries get clean air and water by shifting pollution offshore, not by overall improvements in manufacturing practices.

For this reason, international treaties and trade associations like SEMI and the Electronic Industry Citizenship Coalition have an important role to play. They can set standards and define best practices independent of local jurisdictions. Treaties can establish norms of corporate behavior and insist that countries enforce those norms as a condition of access to the international market. Thus, treaties can help prevent a “race to the bottom” where countries use lax regulations to lure foreign investment. Similarly, if association members agree to hold their supply chains to performance standards, associations can conduct audits to ensure compliance. While they don’t have enforcement powers, they can advocate for model regulations. Like treaties, consistent regulations help ensure that companies can’t gain a competitive advantage by disregarding environmental concerns.

While individual fabs have only limited control over the upstream and downstream parts of the supply chain, life cycle analysis recognizes that each step along the way has room for optimization. Indeed, research at United Nations University found that less than 20% of the energy consumed by an automobile over its useful life is attributable to the original manufacturer. In contrast, integrated circuit manufacturing accounts for roughly 50% of the energy consumed over an average device life, with materials production and final assembly accounting for another 25%. Water consumption and chemical emissions are similarly weighted toward the manufacturing step. Thus, to reduce the environmental impact of cars, reduce the energy consumed by driving. But to reduce the energy consumed by integrated circuits, manufacture them more efficiently.

Many of the typical process improvements that manufacturers would be making anyway can help improve sustainability. Any resources expended to produce wafers that will be scrapped or devices that fail electrical testing are wasted. Thus, as KLA-Tencor director Kara Sherman explained, yield improvements and more rapid yield learning help the fab’s environmental footprint as well as the bottom line. Moreover, the “best” optimization may depend on a particular fab’s circumstances. If a tool is generating hazardous wastes, or if it consumes a resource that is locally scarce — parts of Taiwan are experiencing water shortages, for instance — then wafers lost after that tool may have an especially profound impact on the fab’s sustainability profile.

Few complete analyses of working fabs have been done, at least for public consumption. With the possibility for local exceptions in mind, though, MIT student Matthew Branham found that energy is the largest fab input by a wide margin. As already discussed, the energy-intensive nature of the IC fabrication process suggests that fabs can most effectively reduce their environmental impact by sourcing renewable energy. Indeed, Intel reports that it is the largest voluntary corporate purchaser of green power in the United States.

Part two of this series will consider fab energy use in more detail. Similarly, a future article will consider ways to reduce water consumption — the second largest fab input — both by using less water-intensive processes and tools and by reusing water within the fab. Because the fab’s water supply comes from the immediate vicinity, water use is one of the fab inputs most likely to affect nearby businesses and residents, and most susceptible to action by local regulators. Finally, the last article in the series will consider fab waste, particularly greenhouse gas emissions.

Sustainability is difficult to write about in part because it is a big topic, spanning the entire industry supply chain from quartz sand to retired electronic devices. But it is important to write about for exactly the same reason—it dramatically affects the communities that host fab facilities and ultimately the planet we all inhabit.